Well it has been months since I bought the seat. Haggled with ACM. Tried to get eBay to get involved. Finally bit the bullet and paid the $50.00+ return shipping. ACM did refund the cost of the seat. However, I was down by about $70.00 in shipping costs (both ways).
Strange how it is always the customer that takes the rap. The advertisement was in error. I notice that now they have changed the advert and included the Corbin part number.
Sadly, by the time the refund arrived, the option to leave feedback was not available.
Oh well, once bitten, twice shy.